Girl having trouble eating rare platter (5)
I believe the answer is:
grail
'platter' is the definition.
(grail is a type of cup or platter)
'girl having trouble eating rare' is the wordplay.
'girl' becomes 'g'.
'having' is a charade indicator (letters next to each other).
'trouble' becomes 'ail' (synonyms).
'eating' means one lot of letters goes inside another.
'rare' becomes 'r' (listed by Oxford Dictionary of Abbreviations).
'g'+'ail'='gail'
'gail' placed around 'r' is 'GRAIL'.
(Other definitions for grail that I've seen before include "Cherished goal" , "Holy object of quest" , "Cherished ambition (sought by the Knights of the Round Table)" , "Last Supper cup" , "Arthurian knights' quest" .)